The cottonwood borer, scientific name Plectrodera scalator Fabricius, order Coleoptera can be spotted around host plants during the summer. The beetle is around 1 1/4 inch long with black antennae. The antennae are often longer than the beetles’ body or just as long. The black rectangular areas on a white to yellow background can identify the body of the cottonwood borer. The cottonwood borer larvae have no legs, they are creamy white, and oval shaped. The head is brown to black. The larvae can grow up to 1 ½ inch long.
The cottonwood borer attacks cottonwood trees and other trees and plants. The larvae are among the few that feed on roots. The female adult beetle digs burrows at the base of the host tree. She then deposits eggs in bark. It takes 1-2 years before larvae pupate within larval galleries. Adult beetles emerge from mid-May through early-July.
While cottonwood larvae are not considered pest, the adult cottonwood borer is. The adult beetle can be found on branches and the trunks of many trees such as willow trees, and of course, cottonwood trees. They are very active during the summer months. While cottonwood borer larvae are rarely seen, occasionally, you may cone across one or two. In these cases, chances are, the tree is heavily infested. Sightings usually occur when young trees fall or are killed.
According to AgriLIFE Extension, Texas A&M System, “Young trees may be killed when larvae tunnel under the bark (through the xylem tissue) all the way around the base of the tree, girdling it. More commonly, they structurally weaken the tree causing it to fall over in high winds. Adults feed on leaf stems (petioles) and bark of tender shoots, occasionally causing shoots to break, wilt and die, a symptom called, flagging.”
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